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A pointer a pointing to the memory address associated with a variable b, i.e., a contains the memory address 1008 of the variable b.In this diagram, the computing architecture uses the same address space and data primitive for both pointers and non-pointers; this need should not be the case.
Increment shadow stack pointer 3 Tiger Lake, Zen 3: INCSSPQ r64: F3 REX.W 0F AE /5: RDSSPD r32: F3 0F 1E /1: Read shadow stack pointer into register (low 32 bits) [a] RDSSPQ r64: F3 REX.W 0F 1E /1: Read shadow stack pointer into register (full 64 bits) [a] SAVEPREVSSP: F3 0F 01 EA: Save previous shadow stack pointer RSTORSSP m64: F3 0F 01 /5
A function prologue typically does the following actions if the architecture has a base pointer (also known as frame pointer) and a stack pointer: Pushes current base pointer onto the stack, so it can be restored later. Value of base pointer is set to the address of stack pointer (which is pointed to the top of the stack) so that the base ...
Each can be accessed as two separate bytes (thus BX's high byte can be accessed as BH and low byte as BL). Two pointer registers have special roles: SP (stack pointer) points to the "top" of the stack, and BP (base pointer) is often used to point at some other place in the stack, typically above the local variables (see frame pointer).
x86 word, minimum size of short and int in C −32,768 to +32,767 0 to 65,535 4 bytes 32 bits x86 double word, minimum size of long in C, actual size of int for most modern C compilers, [8] pointer for IA-32-compatible processors −2,147,483,648 to +2,147,483,647 0 to 4,294,967,295 8 bytes 64 bits
Pointer formats are known as near, far, or huge. Near pointers are 16-bit offsets within the reference segment, i.e. DS for data and CS for code. They are the fastest pointers, but are limited to point to 64 KB of memory (to the associated segment of the data type). Near pointers can be held in registers (typically SI and DI).
The OpenVMS Calling Standard on x86-64 is based on the System V ABI with some extensions needed for backwards compatibility. [27] The first six integer or pointer arguments are passed in registers RDI, RSI, RDX, RCX, R8, R9 (R10 is used as a static chain pointer in case of nested functions [ 28 ] : 21 ), while XMM0, XMM1, XMM2, XMM3, XMM4, XMM5 ...
Multiple base registers could be used, for code or for data. Such instructions require less memory because they do not have to hold a full 24, 31, 32, or 64 bit address (4 or 8 bytes), but instead a base register number (encoded in 4 bits) and a 12–bit address offset (encoded in 12 bits), requiring only two bytes.